1. Field of the Invention
The present invention relates to a seal assembly and a crawler-track connection structure.
2. Description of the Related Art
Generally, as shown in FIG. 6, a crawler vehicle such as a construction machine, e.g., a bulldozer tractor or a hydraulic shovel tractor, has an endless link chain 81 and a plurality of ground-contacting shoe plates (not shown) mounted on the link chain 81. The link chain 81 comprises a plurality of links 82a, . . . and 82b, . . . that are disposed parallel to each other, and a crawler-track connection structure 84 for pivotably connecting the links 82a and 82b opposing each other. Specifically, the links 82a and 82b comprise an intermediate portion 85 where the shoe plates (not shown) are mounted, and connecting portions 86 and 87 protruding from the intermediate portion 85. A pin insertion opening 88 is provided in the connecting portion 86, and a bushing insertion opening 89 is provided in the connecting portion 87. The links 82a and 82a and the links 82b and 82b are individually connected together via the crawler-track connection structure 84 such that the connecting portion 86 and the connecting portion 87 are overlapped with each other.
The crawler-track connection structure 84 comprises a pin 90 and a bushing 91 externally fitted around the pin 90. End portions of the pin 90 extend outward from the bushing 91 in the axial direction, and the pin 90 is press-fitted into the pin insertion opening 88 of the link 82. End portions of the bushing 91 are press-fitted into the bushing insertion openings 89. An opening portion of the pin insertion opening 88 on the side of the bushing is formed as a large-diameter portion 92. Space portions 94 are formed by the large-diameter portion 92, an outer end surface of the bushing 91, and an outer peripheral surface 93 of the pin 90. A seal assembly 95 is fitted into the space portion 94. In this case, the bushing 91 is externally fitted to be rotatable around the pin 90, the pin 90 is unitized with the connecting portion 86, and the bushing 91 is unitized with the connecting portion 87. Thereby, end portions of the links 82 and 82 to be connected, i.e., the connecting portions 86 and 87, are pivotably connected together. In addition, an oil injection opening 96 is provided in the pin 90. Oil in the oil injection opening 96 flows to the side of the outer peripheral surface 93 of the pin 90 through a path (not shown) and serves as a lubricant between the pin 90 and the bushing 91.
As shown in FIG. 7, the seal assembly 95 comprises a seal ring 98 having a lip portion 97, a support ring 99 for supporting the seal ring 95, and a load ring 100 for receiving a pressure from the lip portion 97 of the seal ring 98. Thereby, the seal assembly 95 prevents overflow of the aforementioned lubricant to the outside.
In the above-described conventional crawler-track connection structure, to cause the lip portion 97 to press-engage with a corresponding wall (an end surface of the bushing 91 in FIG. 6), the load ring 100 needs to receive a pressure from an outer peripheral side thereof. Therefore, in the conventional structure, housings (space portions 94) need to be formed to insert the seal assembly 95, thereby complicating the overall structure that makes the manufacturing processing to be difficult. In addition, since the seal assembly 95 must be inserted in the space portions 94, the overall assembly requires complicated steps, thereby reducing the productivity.